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MUC1 is expressed at the apical surface of ductal epithelia of tissues, including breast, pancreas, airway, and the gastrointestinal tract, where its functions include lubrication and protection of the epithelia. In addition, roles for MUC1 have been suggested in both adhesive and antiadhesive properties of tumor cells, and extensive O-glycosylation of the MUC1 tandem repeat domain may contribute to these functions. Little information is available on the specific O-glycosylation of MUC1. One problem in identifying different MUC1 glycoforms has been that monoclonal antibodies raised against the MUC1 core protein recognize epitopes in the tandem repeat domain, which is often glycosylated to an extent that obscures these epitopes. We developed an epitope-tagged form of MUC1 that allowed the detection of multiple MUC1 glycoforms and established the presence of a number of important blood group and tumor-associated carbohydrate antigens on MUC1 expressed by two pancreatic tumor cell lines (Panc-1 and S2-013) and two colon tumor cell lines (Caco-2 and HT-29). Antigens detected include sialyl-Lewisa, sialyl-Lewisc, sialyl-Lewisx, and sialyl-Tn.
Burdick et al. (Mon,) studied this question.